Substantial reserves are known to exist of ores, both of the oxidic and sulfidic types, which contain relatively small amounts of nickel and/or cobalt with relatively large amounts of iron. Hydrometallurgical processes for recovering the nickel or cobalt from such ores often entail an acidic leach as the first step, the end product of which is a slurry comprised of a liquor containing small amounts of dissolved nickel and/or cobalt and substantial amounts of hydrated iron oxide solids.
Typically treatment of slurries of this type entails an initial solid/liquid separation step, with settling and decantation or filtration, to obtain a clarified liquor from which the nickel or cobalt can be recovered. The solid/liquid separation step is made awkward by the fact that the iron containing solids tend to be in finely divided form. As a result, the separation contributes significantly to the costs of a commercial operation.